Predetermined torque release hand tool



Feb. 13, 1962 E. F. ETzKoRN 3,020,789

PREDETERMINED TORQUE RELEASE HAND TOOL Filed April l1, 1960 3Shee'bS-Sheet 1 Feb. 13, 1962 E. F. ETzKoRN 3,020,789

PREDETERMINED ToRQuE RELEASE HAND Toor.

Filed April 11, 1960 s sheets-sheet 2 Feb. 13, 1962 E. F. ETzKoRNPREDETEIRMINED TORQUE RELEASE HAND TOOL 3 Sheets-Sheet 3 Filed April l1,1960 E BY United States Patent() 3,020,789 PREDETERMINED TORQUE RELEASEHAND TOOL Elmer F. Etzkorn, Park Ridge, lll., assignor to SkilCorporation, Chicago, Ill., a corporation of Delaware Filed Apr. 11,1960, Ser. No. 21,269 11 Claims. (Cl. 81-52.4)

This invention relates to innovations and improvements in toolattachments which upon being attached to a suitable power tool can beused for driving screws, running nuts, etc.

Tool attachments of this type are known and cornmerically available. Ingeneral, they have a sleeve-like or tubular casing or housing with therear end adapted to be screwed on or otherwise attached to the forwardend of a power tool such as an electric drill and with the front endarranged to receive a tool bit for driving or tightening a fastenerelement. When used for driving screws, a screw driver bit is used andwhen used for running nuts, a suitable socket bit is used.

Usually, these tool attachments are arranged to be driven from the rear,as by means of a shaft projecting therein from the power tool. There issuitable mechanism on the interior of the casing including a spindle,clutches, latching means, springs, etc., so that when the tool isapplied to drive a fastener element, such as a screw, as soon as thedriver has engaged the head of the fastener and pressure or a thrust isapplied, the clutches engage and power is supplied to drive the driver.Driving continues until the screw or nut is tightened to a predeterminedtorque. When this predetermined torque is reached and exceeded, then theinterior mechanism kicks out so that driving torque is no longer appliedto the tool bit and the mechanism runs in a free wheeling or unclutchedmanner until such time as pressure or thrust on the fastener isreleased, whereupon the mechanism recycles. It is known to make suchtool attachments so that they are non-ratcheting whereby when thepredetermined torque has been applied and exceeded and the tool kicksout the mechanism runs completely free with not even a slight draggingtorque being applied to the driver bit or other tool.

The object of the present invention, generally stated, is to providetool attachments of the foregoing type, which are competitive or lowerin price than the presently available devices, and which embody severalimprovements which enhance their utility and eiciency.

More specifically, the object of the present invention is the provisionof new and improved tool attachments of the foregoing type characterizedby improvements and innovations in the following respects and features:each has a hollow spindle which shifts co-axially in certain phases ofoperation; there is shifting or co-axial movement within the casing ofboth the tool bit and also the spindle; the only moving parts in theidling condition are the torque clutch elements; the latching mechanismsfor the anti-ratcheting feature includes a spool member which isslidable within the hollow spindle and acted upon from opposite ends byseparate springs; the torque clutch includes camming means tending toseparate the clutch elements which are in the form of balls permanentlyretained in sockets in oneclutch member and projecting into slantingholes or pockets in the opposite clutch member whereby the balls tend tocam out of such holes with less torque in the driving direction than inthe back-olf direction; and, the torque adjustment for loading the maintorque spring or the torque control spring is of simplified and improvedconstruction.

Certain other objects of the invention will, in part, be obvious andwill in part appear hereinafter.

For a more complete understanding of the nature and ice scope of theinvention reference may now be had to the following detailed descriptionthereof, taken in connection with the accompanying drawings, wherein:

' FIG. 1 is a side elevational view showing a known type of power toolwith a pistol grip, and having a tool attachment constituting oneembodiment of the present invention screwed to the front end thereof;

FIG. 2 is a longitudinal sectional view on enlarged scale, certain partsbeing shown in elevation, through the tool attachment element shown inFIG. v1, the parts being shown in their condition when the toolattachment is idling and the tool bit is not in the engaged or drivingcondition;

FIG. 3 corresponds to FIG. 2 but shows the relationship of the partswhen the driver bit is engaged with a screw and the bit is being drivenby the tool attachment;

FIG. 4 corresponds to FIG. 2 but shows the conditions of the parts theinstant the predetermined torque has been exceeded and the device kicksout;

FIG. 5 corresponds to FIG. 2 but shows the conditions of the parts whenthey are latched in the free wheeling, non-ratcheting condition but withthe tool bit still engaging a screw; v

FIG. 6 is a view on line 6-6 of FIG. 2;

FIG. 7 is a view on line 7-7 of FIG. 2;

FIG. 8 is a detailedv section on line 8-8 of FIG. 7;

FIG. 9 is a detail section on line 9--9 of FIG. 7;

FIG. 10 is a view on line 10-10 of FIG. 2; and

FIG. 1l is a view on line 11-11 of FIG. 3.

Referring to FIG. l of the drawings, a tool attachment representing oneembodiment of the invention is designated generally at 5 in its attachedcondition to the power take-off connection of a power tool indicatedgenerally at 6. The power tool 6 is of known type and does not itselfform a part of the present invention. The power tool 6 has an electricmotor within a housing which includes a pistol grip handle 7, and atrigger control switch member 8. An electric conductor cord by which themotor is connected to a source of electric power is designated at 9entering the underside of the handle 7.

The forward end of the power tool 6 has an interiorly threaded powertake-off opening 10 (FIG. 2) into which an adapter 11 is screwed. Theinterially threaded rear end cup portion 12 of the tool attachment 5 isscrewed onto the adapter 11 as shown in FIG. 2. A drive shaft 13projects from the front end of the tool 6 into the rear end of the toolattachment 5 and serves to drive this attachment in a manner to -bedescribed in detail in connection with FIGS. 2-5.

Referring to FIG. 2, the tool attachment S has a sleevelike or tubularcasing or housing 14 which includes the rear end attaching cup portion12. Desirably, the exterior of the rear end cup portion 12 is providedwith a band of knurling as indicated in FIG. 1 to facilitate attachmentand removal by hand. At the front end, the casing 14 is deformed so asto provide an inturned flange 15 which serves to provide an innershoulder or abutment face and an exterior shoulder and abutment face.

A key component of the tool attachment 5 is a hollow spindle 16. Thespindle 16 is co-axially supported within the casing 14 and isco-axially shiftable in the operation of the tool attachment 5 as willbe described. The spindle 16 is slidably journalled for rotation andco-axial movement at its front end in a bearing 17 in the form of aninturned ange on the inner end of a hollow or tubular threaded member 18which also constitutes a component of the front end assembly means foradjusting the compression on a torque control spring 20.

At its rear end the hollow axle 16 is journalled for rotation andlongitudinal movement in the rear member 21 of a torque control clutchdesignated generally at 22. The rear member 21 constitutes the powerreceiving member of this clutch and the front clutch member 23constitutes the driven member. Both clutch members 21 and 23 areprovided with co-axial bores which accurately fit the rear end of thespindle 16.

The forward end of the power tool shaft 13 is journalled in the innerrace of a ball bearing 24 the outer race of which fits within acounter-bore in the adapter 11 and against an inner retainer ring nut 25which is screwed into the casing end 12. The torque control clutch 22 issuspended between a rear ball bearing ring 26 and a front ball bearingring 27. Both clutch members 21 and 23 are continually biased or urgedtoward the rear of the casing by the torque control spring 20, therebymaintaining the suspension of the clutch 22 between the ball bearingraces 26 and 27.

The torque control spring 20 is under compression and is stationarywithin the casing 14. At the rear end it bears against a at ring member28 which presses against the bearing race 27. At the front end, thespring 20 bears against a pressure adjusting nut 30 which is threaded onthe inner end of the hollow screw member 18 and which is dimensioned tofit slidably within the casing 14. This nut 30 is provided with at leastone longitudinal groove 31 in the outer surface which receives adetented portion 32 of the casing 14. This arrangement prevents the nut30 from turning but allows it to move longitudinally within the casing.It will be seen that by turning the hollow screw member 18 it ispossible to longitudinally adjust the position of the nut 30 and therebyadjust the degree of compression on the torque control spring 20.

The hollow screw member 18 has a circumferential ange or shoulder 33which serves as a shoulder for bearing against the inner face of thefront casing flange 15. The forward end 34 of the sleeve member 18 isprovided with at least two opposed at surfaces for purposes of receivinga wrench to turn the member 18. Adjustment in any particular position ismaintained by means of a jam nut 35 which fits over the outside of themember 18 and screws up against the front end of the casing as shown. Itwill be seen that by loosening the jam nut 35, rotation of the sleevemember 18 will produce shifting of the inner nut 30 either forwardly orrearwardly. After adjustment has been made the jam nut 35 is thentightened. The compression spring 20 Vserves to maintain the front endassembly in the relationship shown with the circumferential ange 33pressing against the inturned flange 15 on the casing.

Returning to the torque control clutch 22 (FIG. 2), cam means areprovided for drivingly interconnecting the power-receiving clutch member21 with the driven clutch member 23. The preferred Iform of this cam orcamming means comprises three bearing balls 36-36 disposed between theopposing faces of the clutch members. The balls 36 are set more thanhalf way in their equispaced recesses 37-37 provided therefor as shownin FIG. 2. Normally the driven clutch member 23 is in the closedposition and juxtaposed to clutch member 21. In`

the rear face of the driven clutch member 23 there are six equi-spaceddimples or pockets 38 (FIG. 7), these being shallower than the pockets37. It will be seen that when torque is applied between the clutchmembers- 21 and 23 there will be a tendency for the balls 36 to cam outof the recesses 38 since they are shallower than the recesses 37. Thegreater the torque, the greater this camming tendency.

While there are two sets of the shallow recesses 38 each of which willmate with the deep recesses 37, preferably, the pockets or recesses 38are not co-axially aligned with the straight recesses 37. On thecontrary, the recesses 38 are preferably drilled on a slant or angle asshown in FIG. 8 using a cutting tool having a frustoconical shape andheld so that one Side 419i each recess 38 is vertical with respect tothe face of the clutch member 23 and the opposite side 40 is slanted.This means that with the tool attachment 5 designed to drive screws ortighten nuts having right-hand threads so that the moving partsincluding the spindle 16 turn in a clockwise direction when viewed fromthe rear, the pockets 38 are so inclined that the clockwise drivingwalls 40 thereof are outwardly slanted from the vertical therebyfacilitating the ease with which the balls 36 can be cammed out orrolled out of the shallow pockets 38.

Since, the opposite driving walls 41 of the recesses 38 are straight orvertical, a greater force or torque is required to cam the balls 36 outof the pockets 38 in the counterclockwise direction than in the drivingor clockwise direction. This arrangement of the opposite driving wallsof the pockets 38 is of considerable practical importance in that aftera fastening element, such as a screw or nut has been driven to apredetermined torque, it is not infrequent that the fastening elementhas to be removed or backed oit. Normally, it requires greater baclooior reverse torque to remove a fastening element than the torque to whichit was driven. Accordingly, by having the respective driving walls 40and 41 of the pockets 38 slanted in the manner described, the torquecontrol clutch 22 automatically supplies a greater removing torque inthe counter-clockwise direction than driving torque in the clockwisedirection. Accordingly, it is merely necessary to reverse the motor inthe power tool to remove a fastening element after it has been drivenand no readjustment in torque has to be made.

ln addition to torque control clutch 22, the tool attachment 5 alsoincorporates a positive clutch indicated generally at 42. The positiveclutch 42 is so-named since it is engaged in a positive manner incontradistinction to the torque control clutch 22 which is normallyengaged except when a predetermined torque is exceeded whereupon itbecomes temporarily disengaged. The clutch 42 comprises a collar-likemember 43 which accurately ts the mid-portion of the spindle 16 and islongitudinally slidable thereon, and which has three equi-spaced clutchteeth 44 projecting from the rear end thereof. The teeth 44 are formating or meshing engagement with three equi-spaced teeth 4S carried onthe front side of the driven clutch member 23. The sets of clutch teeth44-44 and 45-45 are shown in driving engagement in FIG. 1l.

The collar like clutch member 43 in addition to carrying the teeth 44also serves as the means for transmitting driving torque from the torquecontrol clutch 22 to the spindle 16. This is accomplished by having themember 43 provided on its interior with three equi-spaced longitudinalgrooves 46 (FIG. 10) which receive the outer halves of sets of balls47-47. The inner halves of the balls are retained in three grooves 48which extend longitudinally on the outer surface of the spindle 16. Itwill be seen that this ball-groove arrangement is the equivalent of aplurality of splines between the collar-like member 43 and the spindle16. Accordingly, whenever the collarlike member 43 is rotated it carriesthe spindle 16 with it. However, the ball-groove arrangement permitsfree and easy sliding movement between the spindle 16 and the member 43.

In addition to the three equi-spaced grooves 46, the interior of thecollar-like member 43 is provided at the rear or right side with acounter-bore or relief 50 (FIG. 3) which in operation of the toolattachment 5 4are periodically engaged by three latching balls 51.

The collar-like clutch member 43 is continually urged to the rear towarda closed or engaging direction, by means of a spring 52 which surroundsthe spindle 16 and is maintained under compression between the frontside (left end) of the collar member 43 and the rear side of acircumferential flange or shoulder 53 on the spindle 16. It will be seenthat when the inner (left) ends of the grooves 46 engage the front orleft-hand ball 47 therein, and the right-hand or rear ball engages therear or right end of a groove 48, the collar 43 is not permitted to movefurther to the rear or right relative to spindle 16 under the inuence ofthe spring 52. In this manner the clutch member 43 is maintained out ofengagement with the clutch teeth 45 formed on the fron-t side of thedriven clutch member 23 when the spindle 16 is in its forward orleft-most position;

The front or left-hand end of the spindle 16 constitutes the tool bitholder. Thus, this end may be hexshaped on the interior to provide asocket for receiving the hex-shaped end 54 of a screw driven bit,indicated generally at 55. Since the hex-shaped inner end S4 litsslidably within the hex-shaped hollow end 56 of the spindle 16, rotationof the spindle produces rotation of the tool bit 55. The innertelescoping movement of the tool bit 55 in the spindle 16 is limited bymeans of the front or left-hand edge of an inner shoulder 57 formed onthe interior of the spindle 16. That is, when the rear end of the toolbit 55 engages the forward edge of the shoulder 57 the tool bit cannotbe shoved or slid further into the spindle and any additional movementof the tool bit 55 to the rear will have to carry the spindle 16 withit.

The tool bit 55 is temporarily retained in the forward end of thespindle 16 against accidental removal by means of a detent ball 58 whichtits in a necked portion 60 of the tool bit. The ball 58 fits through anopening 61 in the end of the spindle 16 which is covered by agarter-like spring or clip 62 retained in a groove 63. This arrangementfor retaining the tool bit 55 in place against accidental removal, butin a way which permits its intentional removal, may be replaced by otherknown retention arrangements.

Preferably the forward end of the Itool bit 55 is sheathed within afinder device of known type including a sheath 64 which is slidablewithin the outer end of the hollow threaded member 18. The forward endof the sheath 64 is provided with an outwardly flared opening 65 whichserves as a guide for placement over a fastener such as a screw head.The sheath 64 is telescopically retained in the member 18 by means of adetent 66 which projects through an opening in the side of a member 18and extends downwardly into a groove 67 in the outer wall of -the sheath64. The detent 66 is continually pressed inwardly under the force andurging of a garter spring or clip 68 retained in a groove 70. The sheath64 is continually urged to its outer position by means of a compressionspring 71 which is retained between the forward face of the bearingshoulder 17 and the rear end of the sheath 64. The right-hand or innerend of the slot 67 constitutes a stop which prevents the spring 71 frompushing the sheath 64 completely out of the end of the member 18.

The hollow spindle 16 contains mechanism on the interior for the purposeof actuating the latching balls 51 into the latching recess 50 in thecollar-like clutch member 43. This mechanism comprises a plunger 72which has a shoulder 73 on its inner or right end which ts the innerbore of the spindle 16 and which engages tne inner side of the shoulder57 so as to stop the outer or forward movement of the plunger 72.

On its inner or right-hand end the plunger 72 carries a plunger rod 74on which slidably its a spool member 75 the right-hand end of which isreduced in diameter so as to provide a truste-conical cam surface 76intermediate the reduced end portion and the full diameter portion whichis sized to slide within the bore of the spindle 16. At the inner orright-hand end the rod 74 slidably projects through a washer member 77which lits against the inner counter-bored rear end of the spindle 16.The collar 77 is held in place by means of a compression spring 78 intothe outer end of which is inserted the stem portion of a button. Theouter rounded surface of the button 80 is engaged by the inner end ofthe power shaft 13 as shown. The spring 78 also serves the purpose ofbiasing the 6 spindle 16 to the front or left so as to normally hold theshoulder 53 on the front end in engagement with the bearing shoulder 17of the member 18. The tip end of the rod 74 is provided with a smallgarter spring 81 which holds the washer 77, spring 83, spool 75 andspring 82 in place on the rod 74.

The spool member 75 is engaged from both ends by compression springs.From its front or left-hand end it is engaged by one end of acompression spring 82 which lits over the rod 74 with its opposite endengaging the rear or right-hand side of the plunger shoulder 73. Therear or right-hand end of the spool member 75 is engaged by one end of acompression spring 83 which lits over the rod 74 and which is compressedfrom its opposite end by means of the washer 77. The spring 82 is undergreater compression than the spring 83 when the parts are in therelative positions shown in FIGS. 3-5 so that the spool member 75 isbiased or resiliently pushed to the rear or right.

'In use, the tool attachment \5 operates as follows: Assuming that thetool attachment is in place on a power tool 6 as shown in FIG. 1, thetrigger 8 is pressed so as to energize the motor and thereupon the powershaft 13 is driven in a right-hand direction so that the powerreceivingclutch member 21 is driven in a clockwise direction as viewed from therear, i.e. looking toward the left as shown in FIG. 2. The driven clutchmember 23 is also rotated with member 21 through the camming balls 36but otherwise the mechanism on the interior of the housing or casing 14is all stationary. This is important in that it keeps wear to a minimum,and also minimizes the drag placed on the power tool.

The tool is now manipulated so that the finder 64 approaches the head ofa screw for telescopic movement over it. Upon pressing of the toolattachment against the screw, the head enters the opening 65 and centerstherein with a result that further pressure causes the nder sheath 64 tomove to the rear against the force of the compression spring 71 to theposition shown in FIG. 3. When the tip of the driven bit 55 engages thescrew slot, additional pressure causes the tool bit 55 to moverearwardly with the sheath 64 with the result that the rear end 54 ofthe tool bit engages and depresses the plunger 72, thereby unseating itand moving it rearwardly within the hollow spindle 16.

Up to this point the torque control clutch 22 has been rotating butother parts of the mechanism remain stationary. However, when the innerend 54 of the tool bit engages the shoulder 57 further pressure on thescrew causes the spindle 16 itself -to shift rearwardly to the rightagainst the force of the compression spring 78. As this shifting of thespindle 16 occurs it permits each set of balls 47-47 to follow theshifting movement, and the compression spring 52 forces the positivecollar-like clutch member 43 to also shift to the rear.l Upon sufcientshifting movement it will be seen that the teeth 44 on the collar-likemember 43 engage the teeth 45 on the driven clutch member 23 which isrotating. Preferably the driving faces of the clutch teeth on thepositive clutch 42 are so slanted that once there is engagement theteeth tend to cling together rather than to separate. After the teeth 44bottom with the front face of the driven mem- Iber 23 the spindle 16 isstill permitted to move somewhat to the rear or right if continuedpressure is exerted.

Since the spool member 75 cannot move to the right because it isrestrained by the balls 51, the rearward movement of the plunger72-serves to compress the spring 82 to the condition shown in FIG. 3 andspring 78 is also compressed.

Withthe positive clutch 42 engaged it will be seen that the spindle 16is now driven and in turn this drives the driver bit 55 and the screw orother fastener. The driving continues until such time as the fastener isdriven to the point where the torque exceeds the predetermined torquefor which the clutch 22 is set by means of adjusting the compression orpressure on the torque control spring 20. When this torque is exceededthe balls 36 cam out of the set of shallow recesses 38 in which theyhappen to be in by rolling out over the forwardly inclined sides 40(FIG. 8). The position of the parts when this camming out occurs isillustrated in FIG. 4. The main result of the camming out is themovement of the driven clutch member 23 to the front or left against theforce of the spring 20. This shifting movement also causes thecollar-like positive clutch member 43 to shift to the front or left, thedistance of movement being sufficient to bring the latch recesses 50over the latch balls 51 which move into the recesses 50 as shown in FIG.4. The balls 51 are snapped out when the latch recess 50 permits it tobe, by reason of the camming surface 76 on the spool member 75 which isbeing urged to the rear by the compressed spring 82.

The parts assume the condition illustrated in FIG. 4 in an instant andremain in this condition only an instant.

As soon as the balls 36 are rotated to bring them into mating engagementwith the next set of shallow recesses 38 in the now stationary drivenclutch member 23, the driven clutch member immediately snaps closed withthe clutch member 21 and is again driven with it. The condition of theparts when the driven clutch member 23 closes with the power-receivingclutch member 21 while the positive clutch member 43 is retained in itscaught or inoperative position is illlustrated in FIG. 5. It should benoted that the distance which the driven clutch member 23 and thecollar-like clutch member 43 shift when the balls 36 cam out of thepockets 38 is greater than the length of the clutch teeth 44 with theresult that the clutch teeth 44-44 and 45-45 are completely separatedwhen the member 23 resumes its engaged position. Hence there is nodragging movement whatever placed on the spindle 16. As long as pressureis maintained on the tool attachment and against the screw head theparts will stay in the position shown in FIG. wherein only the torquecontrol clutch 22 is operating and all of the other parts arestationary. Thus there is no ratcheting action of the tool once it haskicked out after the predetermined torque has been exceeded.

Upon release of the pressure against the fastener head the springs causethe parts to resume the positions shown in FIG. 2. Thus, as soon as theplunger 72 is permitted to recede by moving forward on the spindle 16,and when the spindle itself moves to the front to its normal position,the spool member 75 will be no longer retained in the position shown,and each latch ball 51 will be forced into its normal inner position bythe collar 43 releasing the collar-like clutch member 43 so that it isonly retained from closing by means of the sets of balls 47.

It will be appreciated that certain changes may be made in theembodiment of the invention above-described and shown in the drawings,and that other embodiments of the invention may be made, Withoutdeparting from the spirit and scope of the invention as reflected in theappended claims.

I claim:

1. In a tool attachment of the class described for driving andtightening rotary fastener elements, in combination: a sleevelikecasing; a hollow spindle the front end of which constitutes a toolholder; front bearing means in said casing for supporting the front endof said spindle for rotation and co-axial sliding movement within saidcasing; a main torque clutch in the rear portion of said casingcomprising a power-receiving clutch member, a driven clutch member, andcompletely disengageable camming means normally directly interconnectingsaid clutch members and tending to separate said driven clutch memberfrom said power-receiving clutch member, said clutch members havingco-axial spindle-receiving openings therein with the rear end of saidspindle being slidable and rotatable therein; spring means within saidcasing resiliently urging said driven clutch member into 8 drivingengagement Vand resisting separation by said cai-nf ming means until apredetermined torque value is exceeded; and, secondary clutch means fordrivingly connecting said power-receiving clutch member with said hollowspindle when said tool is driving a fastener element.

2. The combination called for in claim 1, wherein said camming meanscomprises ball members rotatably disposed in relatively deep individualpockets in the clutch face of one of said members and rotatable inindividual shallower mating recesses in the other of said members.

3. The combination called for in claim 1 wherein said spring meanscomprises a compression spring compressed between stationary parts, anda ball bearing ring is interposed between the front face of said drivenclutch member and the stationary part adjacent thereto.

4. A tool attachment of the class described for driving and tighteningrotary fastener elements, comprising: a sleeve-like casing; a hollowspindle the front end of which constitutes a tool holder; front bearingmeans in said casing for supporting the front end of said spindle, forrotation and co-axial sliding movement within said casing; a torqueclutch in the rear portion of said casing comprising, a power-receivingclutch member, a driven clutch member in front of said rst clutchmember, and camming means normally interconnecting said clutch membersin driving relationship and tending to separate said driven clutchmember from said power-receiving clutch member, said clutch membershaving spindle-receiving co-axial openings therein with the rear end ofsaid spindle being rotatable and slidable therein; first spring meanswithin said casing resiliently urging said driven clutch member intodriving engagement and resisting separation and disengagement by saidcamming means until a predetermined torque value is exceeded; a positiveclutch for driving said spindle, comprising iirst engaging means on thefront side of said driven clutch member and a collar-like clutch memberslidably mounted on said spinde in front of said driven clutch memberand having second engaging means on the rear thereof for interengagingsaid rst engaging means; coupling means interconnecting said spindle indriven relationship with said collar-like clutch member; second springmeans resiliently urging said collar-like clutch member into drivenre'ationship with said driven clutch member; and latch means for holdingsaid collar-like clutch member temporarily out of engagement with saiddriven clutch member against the force of said second spring means, saidlatch means being actuated by tool pressure and being tripped on releaseof tool pressure.

5. A tool attachment of the class described for driving and tighteningrotary fastener elements, comprising: a sleeve-like casing; a torquecontrol spring in the forward portion of said casing; means foradjusting the compression on said torque control spring comprising alongitudinally movable nut, means preventing turning of said nut, ahollow screw member threadedly engaging said nut and having a portionprojecting from the front end of said casing for manual adjustment; atorque clutch disposed in the rear portion of said casing comprising, apower-receiving clutch member, a driven clutch member in front of saidfirst clutch member, and cam means normally interconnecting said clutchmembers in driving relationship and tending to separate said drivenclutch member from said power-receiving clutch member, said clutchmembers having center bores co-axial with said casing; a hollow spindle,the front end of which constitutes a tool holder and is journalled andlongitudinally shiftable in said hollow screw member and the rear end ofwhich is journalled and longitudinally shiftabfe in said bore in saidpower-receiving clutch member with said driven clutch member beingslidable and rotatable thereon; said torque control spring compressedbetween said nut and said driven clutch member resiliently holding thelatter in driven engagement with said power-receiving clutch memberuntil a predetermined torque value is exceeded; a positive clutch fordriving said spindle comprising, first engaging means on the front faceof said driven clutch member, and a collarlike clutch member slidablymounted on said spindle in front of said driven clutch member and havingsecond engaging means on the rear face thereof for interengaging saidfirst engaging means; coupling means interconnecting said spindle indriven relationship with said collar-like clutch member and allowingco-axial movement therebetween; second spring means surrounding saidspindle and compressed between the front side of said collar-like clutchmember and stop means on said spindle for resiliently urging saidcollar-like clutch member into driven relationship with said drivenclutch member; third spring means resiliently urging said spindle in itsforward position; and, latching means for holding said collar-likeclutch member temporarily out of engagement with said driven clutchmember against the force of said second spring means comprising, a spoolmember co-aXially slidable within the mid-portion of said spindle andhaving a cam surface at the rear end thereof, a plunger member in thefront end of said spindle and engageable by the rear end of a tool heldtherein, fourth spring means compressed between said spool member andsaid plunger urging said spool member to the rear and said plunger tothe front, and at least one cammed latch member retained in a window insaid spindle member covered by said collarlike clutch member with alatching recess in alignment therewith, said latch member being urgedout through said window when said plunger is pressed in by the tool andmoving out to its latching position when said collarlike clutch membermoves suiiiciently toward the front for said latching recess to passover said window, and said latch member remaining in the latchingposition until tool pressure on said plunger is released.

6. The tool attachment of claim wherein said means for preventingturning of said longitudinally movable nut comprises a detent in saidcasing and a detent-receiving slot in the surface of said nut alignedwith the axis of said casing.

7. The tool attachment of claim 5 wherein said cam means drivinglyinterconnecting said torque control clutch members comprises a pluralityof bearing balls retained for rotation in relatively deep sockets in theface of one of said clutch members with the projecting portions of saidballs received in relatively shallow mating sockets in the face of theother clutch member, the side Walls of said shallow recesses beinginclined in the direction of driving rotation to facilitate camming outof said balls and the opposite side walls being approximately straight.

8. The tool attachment of claim 5 wherein said coupling means betweensaid collar-like positive clutch member and said spindle comprises aplurality of splining balls retained partly in grooves in the surface ofsaid spindle and partly in grooves in said collar all of said groovesbeing aligned with said spindle, said grooves having end walls allowinglimited relative co-axial movement of said collar-like clutch member andsaid spindle.

9. The tool attachment of claim 5 wherein said third spring meanscomprises a compression spring disposed within a counterbore in the rearend of said spindle and a button seated in the rear end of said springfor engagement by the end of a drive shaft projecting into saidpowerreceiving clutch member.

10. The tool attachment of claim 5 wherein said plunger member has a rodprojecting rearwardly on which said spool member is slidable, and thereis a lifth spring cornpressed between the rear end of said spool memberand a backing member on the rear end of said spindle.

11. In a tool attachment of the class described for driving andtightening rotary fastener elements and the like, clutch meanscomprising a power-receiving clutch member, a driven clutch member,means supporting said clutch members for co-axial rotation with at leastone being co-aXially shiftable relative to the other, the opposing faceof one of said clutch members having a plurality of relatively deepsockets therein for receiving bearing balls so that less than half thesurfaces of said balls project therefrom, the opposing face of the otherof said clutch members having a plurality of relatively shallow socketstherein for receiving said balls so that more than half the surfaces ofsaid balls projected therefrom, a plurality of balls retained in saidrelatively deep sockets, and spring means urging said clutch memberstoward each other, the driving side walls of said shallow recesses beingoutwardly inclined in one direction of rotation of said clutch and beingoverhung in the opposite direction of rotation.

References Cited in the le of this patent UNITED STATES PATENTS1,855,456 Miller Apr. 26, 1932 1,881,633 Johnson Oct. 11, 1932 2,263,709Van Sittert Nov. 25, 1941 2,743,636 Shal May 1, 1956 2,857,997 TraybillOct. 28, 1958 2,886,075 Skoog May 12, 1959 2,923,191 Fulop Feb. 2, 19602,948,173 Herrmann Aug. 9, 1960

